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Activity Number 6 - Smog Prediction


To allow students to apply what they have learned to predicting smog levels in their area.


  • Required from Tomorrow's Forecast:
    • Temperature
    • Wind speed and direction
    • Precipitation forecast
    • Sky cover
  • Today's Air Quality Reading
  • Answer Chart (included on page 18)


Have students answer the following questions and make a prediction about tomorrow's ground-level ozone readings. They should be able to determine if the reading will be higher or lower than today's based on what the weather forecast for tomorrow is.

Things to Think About:

Is the afternoon temperature expected to be greater than 20°C? Ozone formation occurs more readily at these higher temperatures.

Are the winds going to be light, moderate or strong? Light winds usually correspond to increased smog levels since there is limited mixing in the lower atmosphere.

What direction is the wind coming from? Central and Eastern Canada: A southwesterly wind will typically increase smog levels, especially in areas influenced by long-range transport. On the other hand, a northerly wind can decrease smog levels by bringing a cleaner "brand" of air into the area. Southern British Columbia: Winds from the Pacific Ocean and Strait of Georgia push pollutants inland up the Fraser Valley e.g. towards the Abbotsford and Chilliwack regions. When this is combined with a strong temperature inversion, local and regional air quality will deteriorate. Improvement is usually not expected until there is a significant wind shift or precipitation event. (For example, wind becoming moderate to strong northwesterly after a frontal passage.) Hint: Check the latest Environment Canada weather forecast for your area to see if/when any significant changes in wind direction and/or speed are expected.

Is it supposed to be sunny or cloudy? A sunny day provides the energy from the sun required to interact with pollutants and lead to higher ground-level ozone concentrations.

Will there be any precipitation? In most cases, precipitation will remove pollutants from the air, leading to an improvement in the air quality.

What day of the week is it? Pollutants have a tendency to build up in the air. Over the weekend, there is typically less traffic and other pollution-causing activities so pollutant concentrations are lower. Because of this, at the beginning of the week, smog levels can be lower. At the end of the week, the concentration of pollutants have had a chance to build up through the week and this can lead to higher smog levels.

Are you outside a major city or other industrial center? If there is such a source of pollutants nearby, check the wind direction to see if the wind is coming from that direction. The increased number of people, cars and industry in major cities all contribute to increased levels of smog.

Based on your answers to the above questions, will the smog concentrations be higher or lower or remain the same tomorrow?

Answer Chart

Answer Chart
QuestionSmog level HigherSmog Level Lower
Afternoon Temperature above 20°C?  
Wind-light, moderate or strong?  
Wind Direction?  
Sunny or Cloudy?  
Day of the Week?  
Pollution source nearby?  


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